Unit 686 is a Space Pirate mentioned in Metroid Prime 2: Echoes. An injury report in Bioenergy Production in the Space Pirate mining facility in the Agon Wastes states that he released a Tallon Metroid for use as target practice, and was assaulted by this Metroid. Somehow, he survived the attack, but was left with brain damage that would heal in a cycle. What becomes of Unit 686 is unknown.

Official data

Scan (Bioenergy Production)

"Injury Report 07.200.07
Unit 686 released a Metroid for target practice today: the Metroid then assaulted 686. He should be regaining brain functions in a cycle."

Space Pirates
Pirate Classes	Pirate • Militia • Trooper (Dark) • Shadow • Grenadier • Trooper Pirate • Hussar • Commando Pirate Pirate Commando (Dark) • Commander • Armored • Bruiser • Melee Trooper (Cloaked) Deck Commander • Phazite Armored
Zebesians	Gray • Gold • Silver • Cyborg • Super • Aqua • Hologram
Aerotroopers	Flying Pirate • Aqua Pirate • Armored • Advanced • Assault • -G Dark
Elite Pirates	Phazon Elite • Omega Pirate • EPG-8644 and EPG-8656 • EPG-8701 and EPG-8702
Turrets, Robots, Mines and Drones	Auto Defense • Mega • Despair-Class • Dread-Class • Remorse-Class • "Vigilance" Class • Sentry Drone • Aqua Drone • Cloaked Drone • Preed (Dark) • Puffer Mine • Aeromine • Jumpmine Proximity Mine • Crawltank • Crawlmine • "Jolly Roger" Drone • Phazon Harvester Drone • Pirate Surveillance Drone • Pirate Cargo Drone
Pirate Creatures	Aberax • Atomic • Badger Clover • Berserker Lord • Berserker Knight • Bombu (Pulse/Scatter) • Evir • Gronkat • Korakk Beast • Kihunter (King) • Mimic • Olbap • Scarp • Scritter • Thardus • Urtragian Shriekbat • Zero Shock beast • Thrash-hunters
Pirate Leaders	Ridley • Mother Brain • Kraid (Mini-Kraid) • Dark Samus • Gandrayda • Phantoon • Draygon • High Command • Weavel • Sylux Pirate Boss • Boss • Dragüd • Doruba
Pirate Characters	Bug Brain • Chief Astrogation Officer • Commando unit 87 • Experiment 7526 • P-1 • Technician 12 • Units 013 and 043 • Unit 686 • Rundas • Ghor • Gandrayda • Aurora Unit 313
Locations	Agon Mining Facility • Glacier One • Pirate Homeworld • HQ • Tourian Citadel • Metroid
Organizations	Facility Command • Project Helix • Project Titan • Removal Squad • Security Command • Science Team • Sympathisers • Special-forces unit • Team Sclera Planteers of Krom
Miscellaneous	Assault on the Pirate Homeworld • Class Platinum-AAA threat level • Code Blue • Crane • Datanet • History • Lotus Milestone • Metroid project "Dread" • MB • Rotation Control Unit • Command Network • Gallery • Language • Boarding Pod • Crate Kraid's Missile Gun